The present invention relates to a process for preparing at least one cyclic diamine, comprising the reaction of at least one cyclic alkene with a gas mixture (G) comprising dinitrogen monoxide to give at least one cyclic ketone and the subsequent conversion of the at least one cyclic ketone to a cyclic diamine. The invention additionally relates to the use of the cyclic diamines with primary and/or secondary amine functions thus obtained to prepare polyamides and polyurethanes.
Processes for preparing cyclic diamines are known in principle from the prior art. For example, FR 1 537 011 discloses a process for preparing cyclic diamines by catalytically hydrogenating aminonitriles which are obtained from bicyclic lactams. The use of the amines to prepare polyamides and polyurethanes is likewise described.
DE 42 10 311 relates to a process for preparing cyclic diamines from symmetric aldazines and ketazines by hydrogenating azine cleavage by means of hydrogen, the hydrogenation being effected in the presence of ammonia and specific catalysts, for example Raney nickel or cobalt catalysts. DE 42 10 311 describes, for example, the preparations performed in this way of isophoronediamine and 3-methylaminocyclohexylamine.
EP 0 394 058 A1 also describes a process for preparing cyclic diamines for preparing polyamides and epoxy resins. This affords the diamines by catalytic hydrogenation of aromatic diamines.
It is known that cyclic diamines, including in particular commercial isophoronediamine (IPDA), can be used in the preparation of polyaddition resins from the group of the epoxy resins, polyurethane resins and polyurea resins. Reference is made by way of example to DE-A 31 37 898 , GB patent 1 515 473 and EP 0 564 818.
The synthesis methods described in the prior art for preparing such cyclic diamines are inconvenient and costly.